Note: Descriptions are shown in the official language in which they were submitted.
CA 02404853 2008-03-12
Photoeng.raved printed data carrier
This invention relates to a data carrier printed by intaglio printing, to the
produc-
tion thereof and to a printing plate suitable therefor and the method for
producing said
plate.
Security documents and documents of value, for example bank notes, shares,
bonds, certificates, vouchers and the like, which must meet high standards
with respect
to forgery-proo.fiiess, are frequently printed by intaglio printing. This
printing process
provides a characteristic printed image that is easily recognizable to laymen
and can-
not be imitated with other common printing processes.
In intaglio printing, surfaces are usually rendered by a line screen, the line
dis-
tance and width determining the color tone or gray value of the surface.
Printed lines
are usually a few tenths of a millimeter wide and separated by unprinted
areas. During
the printing operation, only the depressions formed in the printing plate
surface by
means of etching or engraving carry ink, while the actual printing plate
surface is ink-
free. This is obtained by wiping the printing plate surface free of excess ink
after ink-
ing with a wiping cylinder or doctor blade.
During the actual printing operation the data carrier to be printed is pressed
against the printing plate with high pressure by a pressure cylinder with an
elastic sur-
face. The at least partly compressible data carrier, usually made of paper, is
thereby
pressed into the ink-filled depressions of the printing plate and thus comes
in contact
with the ink. When the data carrier is detached from the printing plate, the
latter pulls
the ink out of the depressions. A printed image produced in this way has
spaced-apart
printed lines or areas that are covered with an ink layer of varying thickness
in accor-
dance with the depth of the printing plate engraving.
The high bearing pressure additionally causes the substrate material to
undergo
an embossing that is also noticeable on the back of the data carrier. If the
engravings in
the printing plate are deep enough, a data carrier printed by intaglio
printing acquires
through embossing and inking a printed image that forms a relief perceptible
with the
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CA 02404853 2007-09-26
sense of touch. In the unprinted surface areas of the data carrier not
carrying ink, the
high pressures during the printing operation act like a calendering, which
leads to
compression and smoothing of the data carrier surface. These features make
prints
produced by intaglio printing distinguishable anytime from prints produced by
other
techniques.
The problem of the present invention is to produce more complex printed
images by intaglio printing with elevated protection from forgery.
The inventive data carrier is characterized by a surface printed by intaglio
printing and at least one partial surface completely enclosed by said surface,
the
surface and partial surface being printed with the same ink but having
different ink
layer thickness so that they contrast visually. A sign represented by the
partial
surface can be any geometrical element with an e.g. circular, triangular,
square or
asymmetric contour structure, a pictograph, character or other symbol,
preferred
characters being in particular alphanumeric characters.
The printed surface and partial surface enclosed thereby on all sides are
printed
with an ink layer of varying thickness. Since usual intaglio inks are
transparent and
translucent to a certain degree, suitable layer thicknesses and an expedient
choice of
background color will result in color or gray tones of varying brightness and
color
saturation. If there is a sufficient difference of the ink layer thicknesses
of adjacent
surfaces, readily visible contrasts will result for the human eye without
further aids.
Normal lighting conditions and a normal viewing distance are assumed here.
The printed surface and partial surface enclosed thereby are in exact register
if
their position relative to each other is predetermined and adhered to exactly
and
reproducibly without the slightest deviations. If two printed images produced
by
successive, mutually independent printing operations are superimposed, this
exactly
registered positioning of the two surfaces is not possible.
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CA 02404853 2002-09-25
In a preferred embodiment, the printed surface and partial surface are distin-
guishable not only visually by reason of their contrast but also with the
sense of touch,
i.e. tactilely. The surface relief produced by the pressure is composed of an
embossing
of the substrate material and the applied ink layer. The total height of the
relief is
based on the normal, i.e. unprinted and unembossed, data carrier surface and
is at least
25 microns for feelable areas. Relief heights of more than 40 microns are
especially
preferred since surface elements with such relief heights are especially well
percepti-
ble tactilely.
Inventive data carriers have elevated forgery-proofness since the
characteristic
intaglio printed image makes them unreproducible by common printing processes.
If
they also have tactilely perceptible surface elements, this provides
additional effective
protection against imitation by color photocopying or scanning of the data
carriers.
In an especially preferred embodiment, the printed surface of the data carrier
ad-
ditionally encloses unprinted partial areas that can in turn have the form of
one or dif-
ferent signs of any kind. This permits a third piece of information to be
rendered in
negative representation, i.e. by unprinted areas in printed surroundings, in
addition to
the two pieces of information rendered in positive representation, i.e. with
inking, in
the same surface.
According to a further embodiment, the printed surface can also enclose a
plural-
ity of partial surfaces that either all have the same or different ink layer
thicknesses. It
is likewise possible to provide unprinted areas in the partial areas.
The form of the partial surfaces can be selected at will according to the
invention,
for example in the form of geometrical patterns, logos or alphanumeric
characters.
The various partial surfaces, unprinted areas and the contour form of the
printed
surface can also be semantically related. For example, it is possible to
execute the
printed surface in the form of an alphanumeric character and execute the
partial sur-
faces and any unprinted areas present in the printed surface and/or partial
surfaces in
the form of the same sign. If a plurality of printed surfaces are provided on
the data
carrier that together represent a readable piece of information, such as a
multidigit
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CA 02404853 2002-09-25
number or a word, the partial areas and/or unprinted areas within a printed
surface can
also be executed in the form of this total information. But any other semantic
relations
are also possible.
The arrangement of the partial surfaces within the printed surface is as
desired
and subject only to the restriction that the partial surface or surfaces are
largely en-
closed by the printed surface. If only one partial surface exists within the
printed sur-
face, it can for example represent the same information as the printed surface
and ex-
tend within the printed surface parallel to the outside contour. Preferably, a
plurality of
partial surfaces are disposed in the printed surface, however. The smaller the
partial
surfaces are, the greater the number of said partial surfaces can of course
be. They can
be disposed in the printed surface in any pattern. This pattern can likewise
be readable
information, or only a regular column and/or row arrangement. If unprinted
areas are
additionally provided in the printed surface, they can be disposed
altematingly with
the partial surfaces.
In the inventive data carriers, unprinted areas and surfaces with varying ink
layer
thickness adjoin directly and in any order. This makes it possible to render
very com-
plex printed images and superimpose a plurality of pieces of information, also
in posi-
tive representation, on the same surface. The freedom of design in preparing
and ren-
dering printed images produced by intaglio printing is thus enormously
increased.
The inventive method for producing corresponding printed data carriers has in
addition considerable economic advantages since the surfaces provided for
printing
with different ink layer thicknesses are produced with the same ink in one
printing
pass. Suitable substrate materials for printing with the inventive method are
all those
that can be used for intaglio printing, such as paper, plastic foils, paper
laminated with
plastic foils or lacquered paper, and multilayer composite materials.
The inventive intaglio printing plates are preferably produced by engraving
with
a fast rotating, tapered graver. In accordance with the contour form of the
surface to be
printed, corresponding depressions are formed in the surface of the printing
plate by
the engraving tool with selective variation of the engraving depth and are
filled with
ink for the printing operation. During printing, the ink is transferred from
the depres-
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CA 02404853 2002-09-25
depressions of the plate to the surface of a substrate. No ink is transferred
from the un-
treated, i.e. unengraved, surface areas of the printing plate. Deep engraving
of the
printing plate produces a high embossed relief with a thick ink layer on the
printed
substrate, while flat engravings produce only a low embossed relief with a
thin ink
layer. If translucent inks are used, different ink layer thicknesses result in
visually con-
trasting printed surfaces that are distinguishable even when they directly
adjoin.
In order to prevent directly adjoining ink layers from flowing into each other
along their borderline after being transferred to a data carrier and before
the ink has
dried, a so-called "separation edge" is integrated into the printing plate
between sur-
faces with different engraving depth. Said separation edge has a tapered,
wedge-
shaped cross-sectional profile. The tip of the wedge is preferably located at
the height
of the printing plate surface or slightly thereunder.
The tip .of the separation edge profile forms a largely one-dimensional line
along
the separation edge, similar to a knife edge. It separates the printing plate
areas of
varying engraving depth but produces no visible interruption of the printed
ink sur-
faces. With the support of the separation edge integrat6d into the printing
plate, the
intaglio ink, which is of pasty consistency, is left "standing" in
dimensionally stable
fashion after being transferred to a substrate even when surfaces printed with
varying
layer thickness directly abut. In this way, extremely fine,. superimposed
structures with
varying ink layer thickness and high edge sharpness can be printed by intaglio
print-
ing.
When engraving the printing plate, the engraving tool is guided so that a
tapered
separation edge is left standing between the adjoining surfaces having a
different
engraving depth. If a printed partial surface is completely enclosed by a
likewise
printed surrounding surface on the substrate, the depression or engraving of
the
printing plate corresponding to the partial surface must be largely enclosed
by a
separation edge. Ideally, the partial surface is completely enclosed by the
separation
edge.
If the engravings of the printing plate are not, or at least partly not,
inked, that is,
filled with ink, before the printing operation, the noninked area of the
printing plate
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CA 02404853 2002-09-25
acts only as an embossing plate which can produce so-called blind embossings
on a sub-
strate during the intaglio printing operation. The embossed elements have
similar
proportions and tactile properties, with the exception of the visual
impression pro-
duced by the ink, as the above-described printed surfaces and partial
surfaces.
Further embodiments and advantages of the invention will be explained in the
following with reference to the figures. The variants described in the
examples relate
primarily to very small partial surfaces. The inventively printed surface and
partial
surfaces can of course also be executed larger, i.e. a few millimeters to
centimeters.
Fig. 1 shows a bank note in a front view,
Figs. 2, 3a, 3b and 4 show details of printed data carriers in cross section,
Fig. 5 shows an intaglio print in a front view with two superimposed pieces of
in-
formation,
Fig. 6 shows a further intaglio print in a front view with three superimposed
pieces of information,
Figs. 7a, 7b and 8 show intaglio prints in a front view with superimposed
infor-
mation and surfaces of varying ink layer thickness,
Fig. 9 shows a further intaglio print in a front view with superimposed
informa-
tion in a positive representation.
Fig. 1 sketchily shows a bank note as data carrier 1. A bank note usually has
dif-
ferent types of prints. The illustrated bank note shows for example printed
image 5
indicating a portrait. Printed image 5 is realized by conventional intaglio
printing,
which means that different color tones or brightnesses are rendered by line
screens
with varying line distance or line width. Further, background pattern 7 of
fine lines
produced by offset and serial number 8 applied by letterpress are present.
In the example shown here, the inventive print is provided only in a partial
area
of the bank note and consists of surface 2 completely printed with ink and
completely
enclosing partial surface 3 likewise printed with a unified ink layer.
Surfaces 2 and 3
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CA 02404853 2002-09-25
have been printed by intaglio printing with ink layers of varying thickness,
which
makes them visually distinguishable since there is a brightness or color
contrast be-
tween surface 2 and partial surface 3. Additionally, printed surface 2
encloses un-
printed partial areas 4, which can convey further information if they are
designed ac-
cordingly.
In contrast, according to the prior art, infornation is only represented as
printed
surfaces against an unprinted background, i.e. in positive representation, or
as an un-
printed surface against a printed background. Fig. 2 shows in cross section a
data car-
rier area printed according to the prior art, wherein substrate 9 has been
printed with
ink in spaced-apart surfaces 10. In positive representation, the actual
information is
rendered by printed surfaces 10 that stand off in high contrast from unprinted
sur-
roundings 11 and 12. In negative representation, the information is rendered
by un-
printed surface areas 11 while printed surfaces 10 form the surroundings and
enclose
information-conveying unprinted areas 11. Ink-carrying surfaces 10 are usually
lines
with a width of clearly less than one millimeter in conventional intaglio
printing.
Figs. 3a and 3b illustrate the inventive principle of rendering information in
a
continuously printed surface by selective variation of ink layer thickness
between two
layer thickness levels. Figs. 3a and 3b show in cross section a data carrier
area printed
according to the invention. In partial surfaces 14 completely enclosed by
surrounding
print area 13 (which is not recognizable in cross section), the ink layer
thickness varies
so clearly that a visually well perceptible color or brightness contrast
arises between
surfaces 13 and 14. In Fig. 3a, partial surfaces 14 have a greater ink layer
thickness in
comparison to their surroundings, while Fig. 3b shows the reverse case, i.e.
surround-
ing surface 13 is printed with a thicker ink layer than partial surfaces 14.
If transparent
ink is used for producing surfaces 13 and 14, the surfaces with the smaller
ink layer
thickness appear in a lighter color tone. In this case, partial surfaces 14
shown in Fig.
3a stand out as darker surfaces against a lighter background, while partial
surfaces 14
shown in Fig. 3b appear in a lighter color tone than surrounding printed
surface 13.
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CA 02404853 2002-09-25
Information can thus be represented by printed, i.e. ink-carrying, partial
surfaces
14 against likewise ink-carrying surroundings 13. If the shape and contour of
printed
surface 13 likewise conveys information, two superimposed pieces of
information can
be rendered in positive representation on the same surface.
Fig. 4 likewise shows in cross section a detail of an inventive data carrier.
Here,
the printed surface additionally has unprinted partial areas 15 integrated
therein that
are completely enclosed by printed surfaces 13 and 14 (which is again not
recogniz-
able in cross section). If unprinted areas 15 are designed accordingly, these
areas can
render further, additional information in negative representation.
The following Figs. 5 to 9 show enlarged representations of different,
preferred
embodiments of the invention in a front view. For reasons of clarity, only the
printed
image produced by intaglio printing according to the invention is shown. The
ratios of
size of the surfaces to the partial surfaces are rendered realistically.
In Fig. 5 the number "2000" is rendered, each individual digit being
represented
by inventively printed surface 13 having a unified ink layer of a certain
layer thick-
ness. Each printed surface 13 representing a digit contains partial surfaces
14 enclosed
thereby on all sides that have been printed with a thicker ink layer and
therefore appear
darker. The contour form of partial surfaces 14 is selected in this example so
that each
partial surface 141ikewise represents a digit. In Fig. 5, the digit sequence
of partial
surfaces 14 renders the same number as rendered by the sequence of individual
print
areas 13. Any other signs, patterns or symbols can of course also be used. If
surfaces
13 are printed with a printing plate having for example an engraving depth of
e.g. 15
microns in the corresponding areas, while the partial areas of the printing
plate corre-
sponding to partial surfaces 14 are produced for example with an engraving
depth of
e.g. 100 microns, not only a visually well perceptible contrast arises between
surfaces
13 and 14 of the data carrier but also a feelable level difference. This is
because partial
surfaces 14 printed by deep engravings produce on the data carrier a raised
relief that
can be clearly perceived by feeling with the fingertips.
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CA 02404853 2002-09-25
In Fig. 6, the contour form of printed surfaces 13 renders the number "20."
Each
of the two surfaces 13 represents a digit and contains partial surfaces 14
that are
printed with greater ink layer thickness and therefore perceived darker. The
form of
partial surfaces 14 likewise renders the number "20." Additionally, surfaces
13 printed
with the thin ink layer enclose unprinted partial surfaces 15 that are so
designed as to
likewise render the number "20." Thus, three pieces of information with
matching con-
tent in the present example are rendered on the same surface. Two pieces of
informa-
tion are rendered in positive representation while the third piece of
information is ren-
dered in negative representation. Unprinted areas 15 are disposed like a net
within
printed surface 13 and frame each partial surface 14.
In preferred embodiments according to the representations in Figs. 5 and 6,
the
signs rendered by printed surfaces 13 have a height or size of about one
centimeter.
Signs of this size are still easy to read at a great viewing distance.
Enclosed partial sur-
faces 14 preferably render signs with a size of about one millimeter. Signs of
this size
are still easy to read with the naked eye at a normal viewing distance of
about 20 to 50
centimeters. If additional signs are integrated by _unprinted partial
surfaces, they are
preferably executed as microwriting. The preferred sign size is only a few
tenths of a
millimeter. Such microcharacters are only readable without effort with the aid
of mag-
nifying means, for example a magnifying glass, and constitute an additional
security
feature because such fine structures are not resolved with sufficient
precision by cus-
tomary photocopiers and scanners.
Figs. 7a and 7b show two inventive printed images in which printed surfaces 13
render both characters (the digits "2" and "0") and a geometrical element (a
square).
Printed partial surfaces 14 of this example constitute a surface relief formed
especially
strongly by embossing and applied ink layer and are therefore perceptible also
tac-
tilely. The information represented by partial surfaces 14 corresponds to a
simple
geometrical element in the form of a circle here.
Suitable elements that are especially well perceptible tactilely are in
particular
structures with a geometrically simple contour. The size of the feelable
elements is
preferably a few millimeters and they preferably have a distance apart of at
least about
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CA 02404853 2002-09-25
0.5 millimeters. Unprinted partial surfaces 15 integrated into the printed
surface render
the number "20" in Fig. 7a. A further preferred variant not shown in the
figure is to
render solely the same digit "2" by unprinted partial surfaces 15 in the digit
"2" repre-
sented by printed surface 13, and accordingly form unprinted partial surfaces
15 like-
wise as the digit "0" in the digit "0" rendered by surface 13.
In Fig. 7b, unprinted areas 15 have the shape of characters that follow each
other
in a line and form microwriting. Their information content differs from the
informa-
tion content rendered by printed surfaces 13 and partial surfaces 14. A line
of micro-
writing rendered in negative representation is followed by a line of circles
rendered by
partial surfaces 14 with a thick ink layer. In Fig. 7a, however, the signs
rendered by
unprinted areas 15 and printed partial surfaces 14 are so disposed as to
follow each
other alternatingly in both the vertical and the horizontal directions.
In Fig. 8, the unprinted areas are so disposed in the printed surface that
there is
both first unprinted areas 16 enclosed by a printed surface with small ink
layer thick-
ness, in this case by printed surface 13, and second unprinted areas 17
enclosed by an
ink surface with great ink layer thickness, partial surfaces 14 here. In Fig.
8, first un-
printed partial surfaces 16 render the digits "5" and "0." Second unprinted
partial sur-
faces 17 as well as printed, dark partial surfaces 14 are executed as squares.
In Fig. 9, printed, dark surfaces 13 render the digits of the number "50," the
vis-
ual dark impression being conveyed by a thick ink layer. Partial surfaces 14
enclosed
by printed surface 13 have the form of letters together rendering the repeated
word
"EURO" followed by a"$" sign in each case. They are lighter since they are
produced
by an ink layer with small thickness. The information formed by partial
surfaces 14
within printed surface 13 also extends into the surroundings of printed
surface 13. In
the shown example, the signs formed within printed surface 13 by printed
partial sur-
faces 14 also extend into the unprinted surroundings of surface 13. This
variant can
also be used in the other embodiments.
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